The present invention relates to a system and mechanism for the presentation of audiovisuals applied to the field of information.
The mechanical-electronic audiovisual systems of today consist of cine (moving) and fixed image projectors, the latter being known as "slide projectors" or "film strip" projectors.
In the case of cine, the projection is accomplished by the sequential exposure of the image, frame by frame, presented in a fixed frequency such that the photographic sequence projects images of the same object, adopting however, progressively altering positions. Nevertheless, the sound corresponding to the projected scene is read on a band of the film strip by means of optic or magnetic recording. Consequently, it is necessary to keep the film strip moving, changing static images in order to develop and continue the sound track. This being the case, according to established international standards, 18 or 24 frames per second are consumed, but always with a fixed frequency for reasons inherent in the technique of synchronization of sound and image, demanding therefore, great quantities of film even when projecting a fixed image.
In the case of slide or film strip projectors the projection is accomplished by projecting, also frame by frame, static images, when the frames are changed by a system of levers so that each change of frame is pursuant to a command read on a magnetic or independently perforated tape which is recorded, transcribed on the tape on a track at the side of the corresponding sound.
The projection of the image together with the sound begins with a slide projector coupled to a tape player (external or integrated in the projector) permitting, as can be seen, greatly reduced production costs as compared to cine-sound productions resulting therefore in more intensive use and easier access to the the market. Consequently, the ideal would be the possibility of movement in some scenes at times essential for clarifying the object of the projection and that this movement, or in other words this progressive change of frames were capable of having its frequency programmed in time with the audiovisual. Hence, an audiovisual which is to have such movement should have greater frame storage. Currently developed audiovisual systems handle carousels or magazines of up to 140 frames in the case of slides, which for reasons of movement demand spacious storage area, and up to 72 frames in the case of film strip.
The time intervals between frame changes obtained by these projectors are limited by the mechanical design to one frame every 2 seconds or one frame per second using special external equipment. In order that the audience does not see the frames moving while they are being changed, projection is terminated leaving the screen dark for a period of time of about 2 seconds in the former case and about 1 second in the latter, causing the iris of the eyes to dilate during the change and contract during the projection.